Anatomy and Physiology Unit 5 Test Review
Muscular System (Chapter 6)
Name ______________________________
Hour ____________ Date ______________
1. What are the four functions of the muscular system?
Maintaining posture, generating body heat, stabilizing joints, and producing movement in
conjunction with bones.
2. Fill out the chart below on muscle tissue types.
Muscle Tissue Type
Involuntary/Voluntary
Skeletal
Voluntary
Cell description and specifics
Multinucleated, striated, attach to the
body’s skeleton.
Cardiac
Involuntary
Single nucleus per cell, striated, branching
pattern, separated by intercalated discs.
Only Found in heart.
Smooth
Involuntary
Single Nucleus, non-striated, Spindle
shaped cells, lines the walls of the visceral
hollow and digestive organs.
3. Muscle cells are also known as ___Muscle Fibers_______.
4. Match the words with their appropriate description.
a. Epimysium
1. Connective tissue around a single muscle fiber
b. Perimysium
2. Connective tissue around a bundle of fibers
c. Endomysium
3. A bundle of muscle fibers
d. Fascicle
4. Connective tissue around entire skeletal muscle
e. Fascia
5. On the outside of the epimysium
5. Explain the difference between a tendon and an aponeurosis.
Tendon is a rope-like structure made of dense connective tissue that attached muscles to
bones. An aponeurosis is a sheet-like structure that connects skeletal muscle to skeletal
muscle and also skeletal muscle to other body parts that the muscles act upon.
6. The specialized form of endoplasmic reticulum in a muscle cell is called what? What is its function?
Sarcoplasmic reticulum. It stores the necessary calcium ions that are needed for muscle
contraction and releases it “on demand” when muscles need to contract.
7. What is the plasma membrane of a muscle fiber called? ______Sarcolemma________________
8. First put the following terms in order from outside to inside of the muscle fiber and then describe each.
sarcolemma, myofibril, myofilament, sarcomere.
In order from largest to smallest: Sarcolemma, Myofibril, Sarcomere, Myofilament.
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The sarcolemma is the specialized plasma membrane of skeletal muscle cells.
The myofibril are the largest organelles (ribbon-like) inside the muscle cell (or
muscle fiber), and have alternating bands (A and I) that give the muscle cell its
striated appearance.
The sarcomere is the functional contractile unit of the muscle myofibril (where the
contraction takes place), and are arranged end to end like train boxcars.
The myofilaments are protein filaments (actin: thin and myosin: thick) where the
sliding occurs and where ATPase enzymes are used to break down ATP for energy.
9. Explain each of the following terms: A band, I band, actin, myosin, thin filament, thick filament, myosin
heads (crossbridges). Be sure to include any specifics discussed in class.
Each of the structures of these parts reveals the working structure of the myofibrils. The A
bands are the dark bands in alternation with the light bands or I bands which give the
muscle its striated appearance. Inside each sarcomere, there are thick protein filaments
(myosin filaments) and thin filaments (actin filaments) where the sliding movement occurs
to create an individual sarcomere contraction. The sliding movement of the myosin heads
moving along the actin filaments is what gives the sarcomere its contracting or shorter
appearance (think what happens in crowd surfing, a person is moved along by all of the
hands just like the myosin heads move along the thin filaments to create. Movement). A
sum of all these sarcomere contractions causes muscle fiber contraction. A sum of all
muscle fiber contractions will lead to overall muscle contraction.
10. What does it mean when a muscle is toned? What is occurring?
It means the muscle is through a state of continual, but partial, contraction. The more a
muscle is worked, the more motor units that are working on it in a systematic way. Even
though the muscle is at rest, some fibers are being stimulated to contract (graded response)
at times to maintain strength of muscle.
11. Explain how we build muscle endurance.
We exercise muscles in order to cause more flexibility and more resistance to fatigue. We
accomplish this by increasing the blood supply to the actual muscle (through exercise) and
cause our muscle cells to form more mitochondria so they can store more oxygen. This also
causes our heart muscle to hypertrophy and be able to pump more blood during each
contraction. Also, exercise can lead to better neuromuscular coordination.
12. How does resistance lead to an increase in muscle size?
Resistance is an example of isometric contraction (pitted against immovable object or one
nearly so) and causes an actual increase in the size of individual muscle cells because they
make more contractile thick and thin filaments (not an increase in the number of muscle
cells). There is also an increase in the amount of connective tissue that is needed to
reinforce the muscles.
13. Discuss the functions of irritability and contractility with regard to skeletal muscle cells.
Irritability—the ability to receive and respond to a stimulus
Contractility—the ability to shorten (forcibly) when an adequate stimulus is received
14. What is a motor unit?
A Motor unit consists of one motor neuron and all of the muscle cells/fibers that it
stimulates.
15. Why is it important that nerve cells (neurons) and muscle fibers are arranged into motor units? What are
the advantages of this arrangement?
Motor units consist of a nerve cell and all of the skeletal muscles it stimulates. This
arrangement allows many muscle fibers (cells) to be stimulated to contract at once,
allowing for coordinated voluntary muscle movements.
16. Describe how an action potential is initiated in a muscle cell. Mention the terms motor neuron,
neuromuscular junction, synaptic cleft, neurotransmitter, acetylcholine, sarcolemma, Na+ ions, and
electric current (action potential) in your answer.
The motor neuron meets the muscle fiber at the neuromuscular junction; the space between
the nerve and muscle forms the synaptic cleft. When the nerve impulse reaches the end of
the motor neuron, a chemical neurotransmitter called acetylcholine is released into the
synaptic cleft. When acetylcholine reaches the sarcolemma of the muscle fiber on the other
side, Na+ ions rush in, generating an electric current called an action potential within the
muscle fiber.
17. Explain the mechanism of muscle contraction within a sarcomere in terms of the sliding filament theory.
When muscle cells are activated (as in the previous question) the myosin cross bridges
attach to the binding sites on the actin filaments and sliding begins. Energized by ATP,
each myosin cross bridge attaches and detaches multiple times during a contraction, sliding
the filaments closer together and shortening the sarcomere.
18. Where does the calcium ion (Ca2+) come from in the muscle cell that is necessary for muscle contraction
to occur? Why is the calcium not present in the myofilaments all the time?
The calcium ion is released from the sarcoplasmic reticulum when the muscle cell is
stimulated by a motor neuron. The calcium ion allows the myosin heads to bind to the actin
filaments, which causes the sarcomeres to shorten along the length of the muscle tissue. The
constant presence of calcium in the filaments would not allow the muscle to relax between
contractions, so the calcium must be reabsorbed in the SR between contractions.
19. Explain how calcium and sodium are used differently in the contraction of muscle tissue.
Calcium is stored within the muscle fibers/cells in the sarcoplasmic reticulum. Calcium is
needed for muscle contraction (the more calcium, the more contraction). Sodium is found
outside of the muscle fibers/cells normally but when the muscle fiber/cell is stimulated by a
nerve, the sarcolemma (plasma membrane) becomes permeable to sodium ions. The influx
of sodium generates an electrical pulse called an action potential which tells the muscle that
it needs to start contracting. The action potential causes the release of Calcium from the
sarcoplasmic reticulum.
20. Describe the two ways that graded muscle contractions (graded responses) can be produced.
Graded responses can be produced by: 1) changing the speed of muscle stimulation,
or 2) changing the number of muscle cells being stimulated
21. Explain the three pathways that working muscles use for ATP regeneration:
a. Muscles first use up limited supplies of stored ATP in muscles (4-6 seconds worth)
b. Direct phosphorylation using creatine phosphate
Creatine phosphate transfers its high energy phosphate group to ADP forming ATP
needed for muscle contraction, this lasts approximately 20 seconds.
c. Aerobic respiration
This metabolic pathway that uses oxygen breaks down sugars and fats completely
forming carbon dioxide and water; the released energy is used to build ATP. This
sustains the muscles for hours during rest and exercise.
d. Anaerobic glycolysis & lactic acid formation
When muscle activity is intense, and oxygen and sugars are not being delivered fast
enough to the muscle for aerobic respiration, anaerobic glycolysis takes over,
forming small amount of ATP and producing lactic acid. This occurs rapidly, but
only provides enough ATP for 30-40 seconds of strenuous muscle activity.
22. What is the relationship between muscle fatigue, oxygen debt, and lactic acid accumulation?
Muscle fatigue occurs when the muscle tissue is no longer able to contract even though it is
being stimulated as a result of lack of oxygen (oxygen debt) and the buildup of lactic acid.
23. Compare and contrast isotonic and isometric contractions.
Compare: tension develops within the muscle
Contrast: Isotonic—actin & myosin slide past one another, the muscle shortens, movement
occurs.
Isometric—actin & myosin do not slide past one another, the muscle length stays
the same, no movement occurs.
24. Explain how and why exercise is important for keeping the muscular system healthy.
Regular exercise increases muscle size, strength, and endurance. Exercise also makes
muscles stronger, more flexible, and more resistant to fatigue. This occurs due to increased
blood supply to the muscles, increased amounts of mitochondria, increased oxygen within
muscle, and enlarged cardiac muscle within the heart.
25. Use the terms muscle attachments, origin, insertion, movable bone, and immovable bone in a sentence.
Muscle attachments consist of the origin, which attaches to the immoveable bone, and the
insertion, which attaches to the moveable bone.
26. Name the following body movements that are described below:
a. Bending ankle so that toes are raised
____Dorsiflexion_______________
b. Range of movements that create a complete circle (as opposed to a
rotation of less than 360 degrees)
_____Circumduction______________
c. Narrowing joint angle in sagittal plane (bending elbow)
_____Flexion____________________
d. Increasing angle more than in natural position (bending backwards)
_____Hyperextension_____________
e. Returning a body part to body midline (in frontal plane)
_____Adduction__________________
f. Hyperextending ankle joint so toes point downwards
Plantar Flexion___________
g. Turning a body part on axis (horizontal plane) (turning head from side to side) _Rotation______
h. Turning wrists to put hands into anatomical position ___Supination_______________________
i. Lifting a body part away from body midline (in frontal plane) __Abduction_________________
j. Increasing joint angle in sagittal plane (straightening elbows) __Extension__________________
k. Turning the sole of the foot so it faces laterally __Eversion______________________________
27. Give an example of a complete muscle name that exhibits the following criteria:
a. Direction of muscle fibers
Ex. External oblique ______Transversus abdominis_________
b. Relative size of muscle _______Fibularis longus_______________________
c. Location of muscle ____Tibialis anterior_____________________________________
d. Number of origins _____Triceps brachii_____________________________________
e. Location of origin & insertion __Brachioradialis _Sternocleidomastoid__________________
f. Shape of muscle ___Trapezius_(trapezoid)______________________________________
g. Action of muscle __Flexor digitorum_________________________________________
28. Skeletal muscles to know and be able to label on diagram.
Temporalis
Biceps brachii
Frontalis
Triceps brachii
Masseter
Trapezius
Buccinator
Pectoralis major
Zygomaticus
Latissimus dorsi
Orbicularis oris
Rectus abdominis
Orbicularis oculi
Tranversus abdominis
Sternocleidomastoid
External Obliques
Platysma
Internal Obliques
Deltoid
Intercostal muscles
Gluteus maximus
Gluteus medius
Adductors
Iliopsoas
Quadriceps Group
Hamstring Group
Sartorius
Gastrocnemius
Tibialis anterior
Peroneus Muscles
Label the Diagram to the right.
Sarcolemma
Vocabulary to include:
 Muscle fiber/cell
Muscle Fiber/Cell
 Sarcolemma
 Nucleus
 Myofibril
 Sarcomere
 A/Dark Band
A/Dark Band
 I/Light Band
 H Zone
 Z disk
 Thick (myosin) Filament
Thin/Actin Filament
 Thin (actin) Filament
Myofibril
I/Light Band
Nucleus
Z disk
H Zone
Z disk
Thick/Myosin Filament
A/Dark Band
I/Light Band
M Line
I/Light Band